The main goal of this project is to understand how sensory interneurons represent sensory information in their ensemble response patterns and to understand the biophysical mechanisms through which interneurons extract and encode stimulus features. I will use a combination of modeling, theoretical, and physiological techniques to address the problem. My strategy will be to establish a mechanistic, explanatory model of the neural system, and verify that this model captures the essential behavior of the system by making predictions of system function and testing these through experiment. The essential elements of the study are identification of the "codebook" implemented by sensory interneurons, using physiology and an information theory method, identification of the structural traits responsible for this coding using compartmental modeling and optimization theory, and experimental verification of the role of these structural traits through pharmacology and physiology.